Diff interchangibility M20 <> M50 engined.

[emw525E34]

I have got an '89 M20 engined car that had LSD diff with 4.10 ratio. And my manual 95 Touring (M50TU) has a Open Diff with 4.10 ratio as well. It there a direct swap compatibility ?. Pls advise if anyone has done this or similar. Flange size same ?. Gasket fitment OK ?.

PS: The touring needs LSD more than the sedan ...
:(

[Rigmaster]

Basically, there are 2 different size E34 diffs, the 525i (m20 or M50), 535i, 530i all have the same case and interchange with no problems. On these diffs, there are different input flanges depending on the type of transmission (5 speed or auto)- 5 speed tranny diffs have a larger flange than the auto tranny diffs. The flange can be swapped but you must be very careful to torque the pinion nut to the correct spec or risk damaging the pinion bearing.

That said, you should be able to swap the M20 525i diff right into the M50 525i- as long as they both have the same type tranny. One thing to consider is that cars equipped with ASC (stability control) all have OPEN diffs- they use the brakes to control traction to each rear wheel. I'm not sure what effect, if any, an LSD would have on the ASC system.


Bret.

[emw525E34]

Dang,

My LSD diff is in the M20 with auto tranny while the OpenDiff is on the manual tranny car. So no way to swap ?. Any ways to replace both flanges to match using new flanges ?.

[Rigmaster]

Did you miss this??


The flange can be swapped but you must be very careful to torque the pinion nut to the correct spec or risk damaging the pinion bearing.



Bret.

It's held on with a large nut (30mm??) and a lock plate to keep the nut from coming loose.

I guess you could also just swap the driveshaft from the "donor" car as well as it's diff, that would avoid the need to swap the flange from the old diff onto the "new" diff.

Bret.

[632 Regal]

what you need to know?

http://www.bimmer.info/~regal632/rearend.html